Originally Posted by
AlwaysAisle
Once you made it to the departure lounge area, then you cannot walk back to check-in area and leave the airport like you can do at the U.S. airports.
It's not normal procedure, but it's possible.
That said, there's no airside locked storage for passengers that I'm aware of. You could leave a bag in an open luggage rack at the lounge and hope for the best, but it's almost certainly against the rules and I really don't recommend it.